1. Field of the Invention
Embodiments of the present invention relate to an apparatus for fabricating a semiconductor device and a method of fabricating the same, and more particularly to a photomask and a method of fabricating the same.
2. Description of the Related Art
In order to increase the integration of semiconductor devices, a technique of forming fine patterns having a significantly small critical dimension on a semiconductor substrate is required. To meet this demand, photolithography using a photomask having assist patterns proximal to circuit patterns has been used. Using such a photolithography approach, a depth of focus and a critical dimensional margin of the circuit patterns transferred onto a semiconductor substrate can be increased. The assist patterns are formed on the photomask, but are minimally transferred onto the semiconductor substrate, or are not transferred at all.
FIG. 1 is a sectional view illustrating a conventional photomask. Referring to FIG. 1, a photomask includes a circuit pattern 120 and assist patterns 130 on a transparent substrate 110. The assist patterns 130 of the photomask have too small of a critical dimension to be transferred onto a semiconductor substrate when performing photolithography. Due to the diffraction characteristic of light, the assist patterns 130 are not transferred onto the semiconductor substrate.
However, the forming of the assist patterns 130 having such a minute critical dimension causes several problems during fabrication. For example, resolution restrictions of an apparatus of recording electron beams result in inferior forming of the assist patterns 130. The inferior formation of the assist patterns 130 is a serious problem when analyzing a defect of the photomask. Also, because of the minute critical dimension, the assist patterns 130 can readily collapse when cleansing, etc.